For instance from German Published Patent Application No. 198 49 203, a fuel injector for fuel-injection systems of internal combustion engines is known. It includes a valve-closure member cooperating with a valve-seat body to form a sealing seat, and a piezoelectric actuator for actuating the valve-closure member. The piezoelectric actuator has piezo-layers and one or a plurality of temperature-compensation layers. The temperature-compensation layers have a thermal expansion coefficient whose sign is the opposite of that of the thermal expansion coefficient of the piezo-layers.
Furthermore, from German Published Patent Application No. 199 18 976, a fuel injector for fuel-injection systems of internal combustion engines is known, which includes a first piezoelectric or magnetostrictive actuator, a valve-closure member, which is actuable by the first actuator by means of a valve needle and cooperates with a valve-seat surface to form a sealing seat, and has a second piezoelectric or magnetostrictive actuator, which acts upon the valve needle counter to the first actuator. The actuators are arranged one after another in the longitudinal direction of the fuel injector and are interconnected by a bearing element, which is permanently supported in the fuel injector.
Disadvantageous in the fuel injector known from German Published Patent Application No. 198 49 203 is that the temperature compensation is implemented by special layers within the actuator, the material of these temperature-compensating layers exhibiting thermal expansions acting in opposite directions. This causes problems, in particular during rapid dynamic operations, since the different materials react differently, due to the dissimilar thermal expansion coefficients. Furthermore, a special actuator with temperature-compensation layers must be developed.
A disadvantage of the fuel injector known from German Published Patent Application No. 199 18 976 is the large overall length that the axially offset arrangement of the actuators necessitates. Also, this large overall length goes hand in hand with a widening of the fuel injector, which the support of the bearing plate calls for.